Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$101.96	9.484%	$111.6299	$111.63	$111.65	$111.60
Purchase #2	$195.38	12.713%	$220.2187	$220.22	$220.20	$220.20
Purchase #3	$199.40	5.232%	$209.8326	$209.83	$209.85	$209.80
Purchase #4	$150.35	5.638%	$158.8267	$158.83	$158.85	$158.80
Purchase #5	$199.73	11.602%	$222.9027	$222.90	$222.90	$222.90
Purchase #6	$170.54	7.575%	$183.4584	$183.46	$183.45	$183.50
Purchase #7	$106.41	11.524%	$118.6727	$118.67	$118.65	$118.70
7 purchase totals =	$1,123.77		$1,225.5417	$1,225.54	$1,225.55	$1,225.50